D792 - A save is mounted from the title's own storage

Status: decided Date: 2026-10-11

sceSaveDataMount3 mounts the save its parameters name at /savedata0. The save is the directory of that name under the title's writable /data/savedata, so it lives in the title's overlay and persists as everything else the title writes does (ORBISTOUN_SANDBOX=ephemeral empties it). A mode with bit 2 (create) makes a missing save; without it a missing save answers 0x809f0008. The mount is writable only when the mode has bit 1 (read-write). The result takes the mount point at +0x00, zero required blocks at +0x10 and 1 at +0x1c when the save was created. sceSaveDataUmount2 releases the mount.

Assumed (known_by = assumed): the mode bits, the result layout and the not-found code are the SDK's as public headers give them, used as an oracle. The plugin's own reads confirm only where it looks (result+0x10 u64, +0x1c u32). obSCEne could not bind Mount3 from a homebrew process (REQ-sm02), so a measurement replaces these when one exists.

Why: the user chose it on 2026-10-11 over answering "no save data" and over waiting. PPSA03416's save plugin mounts at start-up and does not go on without it.

Rejected:

• Answering not-found always: the title would try to create and fail the same way.
• A save store outside the title's overlay: a second place to clear and back up.